Elevation and .ns file format?

08-30-2001

Is it possible to have the elevation data stored as well? This would be *really* useful for dumping the data into a mapping program like EDX or Radio Mobile.

I don't think NEMA has an elevation field, but the Garmin Proprietory protocol does.

Also, is there a doc or spec that details the format of the netstumbler data file? I'd like to parse out the raw data instead of relying on the text exports .

I've looked around the site and on the 'net, and unless I'm blind (which i may very well be), I can't find anything.

08-30-2001

I'd really like to see a different format on the export. I'm importing the exproted files into Excel and performing sorts and such, and the differances in spacing between fields plays havoc with that effort.

08-30-2001

I'd really like to see a different format on the export. I'm importing the exproted files into Excel and performing sorts and such, and the differances in spacing between fields plays havoc with that effort.

08-31-2001

Actually it's not NEMA, that's National Electrical Manufacturer's Association. The Data output by GPS units is NMEA, National MARINE Electronics Association.

Big Difference.

NMEA outputs altitude info quite nicely. But be aware that GPS altitude calculation is much less precise than Lat/Lon data, based on current geographic models.

Still an altitude field in NetStumbler would be a somewhat useful addition. However, there really is no way of telling how high the AP antenna actually is based on your reception point. For instance, a local hospital in my area has an AP antenna on a tower on it's roof about 70 feet in the air. The HAAT (height above average terrain) of that antenna is impressive, given I live in a pretty flat area and the hospital is located on a high spot.

Sparky

09-05-2001

Actually it would be helpful for checking the real-world range on an AP.

My understanding of the NEMA protocol is that it does not include the elevation field (I could be wrong though). The Garmin (propietory) protocol does. I saw grayed out fields for Garmin but I have no idea how to turn it on.

09-05-2001

Hmm... It's amzing that people post without reading. First, again there is no NEMA Protocol. There is however, an NMEA Protocol.

Your understand of the protocol must be very weak (or non-existant)since you can't even name the protocol in question properly (even after being corrected once). Furthermore the NMEA standard outputs altitude data quite nicely. Both the Garmin protocol and the NMEA protocal are PUBLISHED standards and it would be very easy for your to READ them, rather than make false assertions. Specifically look to the GGA data sentence that ALL NMEA cabable GPS units output. I have owned at least half-a-dozen GPS receivers, only two of which have been Garmins and all my GPS units have outputted this NMEA string.

And as I pointed out, your best reception point has little to do with the altitude of the AP. A recent article about War Driving in Manhatten points this out. High-rises, hills, and towers all work to stymie attempts at determining AP transmission height. Depending on the situation, the AP may be well above you or well below you.

09-05-2001

Sorry about all the typos in my last response - it was rather early in the AM (for me at least).

From Peter Bennett's GPS and NMEA FAQ Page
http://vancouver-webpages.com/peter/

1. What is NMEA?

The National Marine Electronics Association is dedicated to the
education and advancement of the marine electronics industry and
the market which it serves.

It is a non-profit association composed of manufacturers,
distributors, dealers, educational institutions, and others
interested in peripheral marine electronics occupations
(quoted from a promo in "NMEA News")

-----------------------
Non-proprietary NMEA data sentence with height info:

GGA - Global Positioning System Fix Data
GGA,123519,4807.038,N,01131.324,E,1,08,0.9,545.4,M ,46.9,M, , *42
123519 Fix taken at 12:35:19 UTC
4807.038,N Latitude 48 deg 07.038' N
01131.324,E Longitude 11 deg 31.324' E
1 Fix quality: 0 = invalid
1 = GPS fix
2 = DGPS fix
08 Number of satellites being tracked
0.9 Horizontal dilution of position
545.4,M Altitude, Metres, above mean sea level
46.9,M Height of geoid (mean sea level) above WGS84
ellipsoid
(empty field) time in seconds since last

09-06-2001

> Hmm... It's amzing that people post without reading.
>First, again there is no NEMA Protocol. There is however,
>an NMEA Protocol.

You're one to type, aren't you?

First of all, my understanding of the protocol comes from Garmin's protocol documentation. In my (brief) stint at writing an app to record coordinates from my eTrex, I had to use the D800_Pvt format to transfer the altitude. For whatever reason I read something that led me to the impression that the NEMA^H^H^HMEA protocol did not.

Although your correction to my impression is appreciated, your arrogant and condescending tone is not.

09-06-2001

Well, when you tell someone something and they DENY it, without even bothering to do a little easy fact checking on their own...

I have 6+ years of practical experience in implementing GIS Based WANS and RF Mapping.

09-11-2001

Since the shouting about NMEA's name has died down, the answer to the original question is that the elevation is stored in the binary (NS1) files but it isn't output on the display or in the text files. The reasons for this are (1) it's not as useful as lat/long; (2) if I'm going up and down in a skyscraper then I probably have a really poor GPS fix; (3) I couldn't be bothered to put it in.

09-11-2001

Again, what do you do when you post a God's Honest correction and people deny it? Altitiude info is included in the NMEA data output. The geoidal model of the earth (used by GPS receivers) has serious flaws and are most manifest in altitude reporting. Your reported altitude has little or no bearing on the height or range of a received AP.

Good lord, and then when you associate said info with an organization that concerns itself with the design and manufacture of electrical boxes, circuit breakers, and the like; instead of data output by a GPS...

I suppose when Square D starts making GPS Units and Garmin starts manufacturing electrical panels, it will be more acceptable to blur the two names...

I suppose some of you load bullets into a clip, I load ammunition into a magazine.

blackwave · 05-31-2002

Quote:

Originally posted by Marius
Since the shouting about NMEA's name has died down, the answer to the original question is that the elevation is stored in the binary (NS1) files but it isn't output on the display or in the text files. The reasons for this are (1) it's not as useful as lat/long; (2) if I'm going up and down in a skyscraper then I probably have a really poor GPS fix; (3) I couldn't be bothered to put it in.

Thanks for the hint Marius, some of use were wondering what some of the extra data was...

08-30-2001	#1 (permalink)
Posts: n/a	Elevation and .ns file format? Is it possible to have the elevation data stored as well? This would be really useful for dumping the data into a mapping program like EDX or Radio Mobile. I don't think NEMA has an elevation field, but the Garmin Proprietory protocol does. Also, is there a doc or spec that details the format of the netstumbler data file? I'd like to parse out the raw data instead of relying on the text exports . I've looked around the site and on the 'net, and unless I'm blind (which i may very well be), I can't find anything.

Thread Tools
Show Printable Version Email this Page
Display Modes
Linear Mode Switch to Hybrid Mode Switch to Threaded Mode

08-30-2001	#2 (permalink)
Posts: n/a	I'd really like to see a different format on the export. I'm importing the exproted files into Excel and performing sorts and such, and the differances in spacing between fields plays havoc with that effort.

08-30-2001	#3 (permalink)
Posts: n/a	I'd really like to see a different format on the export. I'm importing the exproted files into Excel and performing sorts and such, and the differances in spacing between fields plays havoc with that effort.

08-31-2001	#4 (permalink)
Posts: n/a	Actually it's not NEMA, that's National Electrical Manufacturer's Association. The Data output by GPS units is NMEA, National MARINE Electronics Association. Big Difference. NMEA outputs altitude info quite nicely. But be aware that GPS altitude calculation is much less precise than Lat/Lon data, based on current geographic models. Still an altitude field in NetStumbler would be a somewhat useful addition. However, there really is no way of telling how high the AP antenna actually is based on your reception point. For instance, a local hospital in my area has an AP antenna on a tower on it's roof about 70 feet in the air. The HAAT (height above average terrain) of that antenna is impressive, given I live in a pretty flat area and the hospital is located on a high spot. Sparky

09-05-2001	#5 (permalink)
Posts: n/a	Actually it would be helpful for checking the real-world range on an AP. My understanding of the NEMA protocol is that it does not include the elevation field (I could be wrong though). The Garmin (propietory) protocol does. I saw grayed out fields for Garmin but I have no idea how to turn it on.

09-05-2001	#6 (permalink)
Posts: n/a	Hmm... It's amzing that people post without reading. First, again there is no NEMA Protocol. There is however, an NMEA Protocol. Your understand of the protocol must be very weak (or non-existant)since you can't even name the protocol in question properly (even after being corrected once). Furthermore the NMEA standard outputs altitude data quite nicely. Both the Garmin protocol and the NMEA protocal are PUBLISHED standards and it would be very easy for your to READ them, rather than make false assertions. Specifically look to the GGA data sentence that ALL NMEA cabable GPS units output. I have owned at least half-a-dozen GPS receivers, only two of which have been Garmins and all my GPS units have outputted this NMEA string. And as I pointed out, your best reception point has little to do with the altitude of the AP. A recent article about War Driving in Manhatten points this out. High-rises, hills, and towers all work to stymie attempts at determining AP transmission height. Depending on the situation, the AP may be well above you or well below you.

09-05-2001	#7 (permalink)
Posts: n/a	Sorry about all the typos in my last response - it was rather early in the AM (for me at least). From Peter Bennett's GPS and NMEA FAQ Page http://vancouver-webpages.com/peter/ 1. What is NMEA? The National Marine Electronics Association is dedicated to the education and advancement of the marine electronics industry and the market which it serves. It is a non-profit association composed of manufacturers, distributors, dealers, educational institutions, and others interested in peripheral marine electronics occupations (quoted from a promo in "NMEA News") ----------------------- Non-proprietary NMEA data sentence with height info: GGA - Global Positioning System Fix Data GGA,123519,4807.038,N,01131.324,E,1,08,0.9,545.4,M ,46.9,M, , *42 123519 Fix taken at 12:35:19 UTC 4807.038,N Latitude 48 deg 07.038' N 01131.324,E Longitude 11 deg 31.324' E 1 Fix quality: 0 = invalid 1 = GPS fix 2 = DGPS fix 08 Number of satellites being tracked 0.9 Horizontal dilution of position 545.4,M Altitude, Metres, above mean sea level 46.9,M Height of geoid (mean sea level) above WGS84 ellipsoid (empty field) time in seconds since last

09-06-2001	#8 (permalink)
Posts: n/a	> Hmm... It's amzing that people post without reading. >First, again there is no NEMA Protocol. There is however, >an NMEA Protocol. You're one to type, aren't you? First of all, my understanding of the protocol comes from Garmin's protocol documentation. In my (brief) stint at writing an app to record coordinates from my eTrex, I had to use the D800_Pvt format to transfer the altitude. For whatever reason I read something that led me to the impression that the NEMA^H^H^HMEA protocol did not. Although your correction to my impression is appreciated, your arrogant and condescending tone is not.

09-06-2001	#9 (permalink)
Posts: n/a	Well, when you tell someone something and they DENY it, without even bothering to do a little easy fact checking on their own... I have 6+ years of practical experience in implementing GIS Based WANS and RF Mapping.

09-11-2001	#10 (permalink)
Posts: n/a	Since the shouting about NMEA's name has died down, the answer to the original question is that the elevation is stored in the binary (NS1) files but it isn't output on the display or in the text files. The reasons for this are (1) it's not as useful as lat/long; (2) if I'm going up and down in a skyscraper then I probably have a really poor GPS fix; (3) I couldn't be bothered to put it in.

09-11-2001	#11 (permalink)
Posts: n/a	Again, what do you do when you post a God's Honest correction and people deny it? Altitiude info is included in the NMEA data output. The geoidal model of the earth (used by GPS receivers) has serious flaws and are most manifest in altitude reporting. Your reported altitude has little or no bearing on the height or range of a received AP. Good lord, and then when you associate said info with an organization that concerns itself with the design and manufacture of electrical boxes, circuit breakers, and the like; instead of data output by a GPS... I suppose when Square D starts making GPS Units and Garmin starts manufacturing electrical panels, it will be more acceptable to blur the two names... I suppose some of you load bullets into a clip, I load ammunition into a magazine.